Bubble Printing of Anisotropic Clay Nanotubes

The printing of colloidal particles with laser-driven microbubbles stands out as a powerful recent technique for rapid fabrication of assemblies with limited sample requirements and a high spatial precision. However, controlling the structure of the resulting printed pattern remains a challenge with anisotropic particles whose orientation can significantly impact the collective properties of the assembled structures. Herein, imogolite clay nanotubes with controlled dimensions and aspect ratio, that also display liquid-crystalline properties in suspension, were chosen as model 1D colloids. In the absence of laser movement, toroidal patterns were formed, with their size and shape strongly influenced by the electrostatic repulsion between nanotubes. Linear patterns printed under stage movement varied significantly depending on the movement speed and colloidal stability. Longer nanotubes in particular exhibited the formation of long filament bundles wrapping the microbubble in a radial orientation. However, insufficient electrostatic repulsion between nanotubes led to poor deposition. Interestingly, the liquid-crystalline dispersions were able to impart optical birefringence to the patterns themselves. This work provides a foundation for future studies on anisotropic nanomaterials, and reveals the potential of bubble printing to retain the light polarization properties of liquid crystalline colloids, which will advance future applications in sensing and devices.